Shock absorbers with compressible cushions



Dec. 10, 1957 E. G. BOEHM ETAL 2,815,829

SHOCK ABSORBERS WITH COMPRESSIBLE CUSHIONS Original Filed March 9, 1951Illu EN@ G. Boei/1772 Carl Z7.' Lau Z H Z H5 United tates Patent O lSHCK ABSUREERS WHTH COMPRESSIBLE CUSHIGNS Eric G. Boehm, Birmingham,Mich., and Carl F. Lautz, Bualo, N. Y., assignors to HoudailleIndustries, Inc., a corporation of Michigan Original application March9, 1951, Serial No. 214,782, now Patent N0. 2,781,869, dated February19, 1957. Divided and this application March 9, 1955, Serial No. 493,315

7 Claims. (Cl. 18S-88) The present invention relates to improvement intelescopic shock absorbers and more particularly concerns improvementsin such shock absorbers affording smoother operation.

The present invention is a division of our copending application SerialNo. 214,782, led March 9, 1951, and now Patent No. 2,781,869.

One of the principal reasons for using hydraulic fluid in direct actingshock absorbers is to take advantage of the incompressibility of thehydraulic fluid. Thereby greater resistance to relative movement of thecylinder and piston portions of the shock absorbers is attained by theproper metering of the hydraulic iiuid in displacement of the iiuid fromchamber to chamber in the shock absorber unit than where a gas or air isused in the shock absorber, with the high compressibility ratio of thegaseous iiuid and generation of heat of compression. However, due to theincompressibility of the hydraulic uid, at least the initial resistanceto relative movement of the piston and cylinder responsive to highmagnitude or frequency shocks is such as to cause some jarringresistance. This lack of smoothness in operation under severe shockconditions is especially noticeable in passenger vehicles.

An important object of the present invention is to overcome the roughriding characteristics of hydraulic direct acting shock absorbers by theprovision of pneumatic cushioning means therein.

Another object of the invention is to provide pneumatic cushioning meansin direct acting hydraulic shock absorbers in such a manner as to adaptthe hydraulic cushioning means to existing forms of the shock absorbersand avoid the necessity of any substantial re-designing of the shockabsorber components.

A further object of the invention is to provide auxiliary cushioningmeans in direct acting hydraulic shock absorbers adapted to be suppliedas optional equipment in such shock absorbers. Still another object ofthe invention is to provide in direct acting hydraulic shock absorberssmall volume gaseous pockets `or cells to afford compressible cushions.

Other objects, features and advantages of the present invention will bereadily apparent from the following detailed description of certainpreferred embodiments thereof taken in conjunction with the accompanyingsheet of drawings, in which:

Figure 1 is a fragmental vertical diametrical sectional view through ahydraulic shock absorber illustrating one embodiment of the instantinvention; and

Figure 2 is a fragmental diametrical Vertical sectional view takenthrough a modified shock absorber structure embodying the invention.

By way of illustration the instant invention is shown as embodied in adirect acting or telescopic shock absorber 11B (Figure l) whichcomprises, as its component parts, a cylinder 11 having reciprocablyoperable therein a piston 12 carried by the lower end portion of apiston rod 13 and dividing the interior of the cylinder into upper andlower pressure chambers 14 and 15, respectively. At

2,815,829 Patented Dec. 10, 1957 its lower end the cylinder isassociated with a foot valve structure 17 including a cage member 18with which the lower end of the -cylinder is concentrically assembledand which in turn is maintained in assembly by the cylinder with a lowerclosure cap member 19 assembled with a reservoir tube or casing 20 oflarger diameter and disposed concentrically about the cylinder 11 andaiording a reservoir chamber 21 between the cylinder and the reservoircasing.

During what is known .as the compression stroke of the piston 12, thatis, when the piston travels downwardly in the cylinder 11 as viewed inFigure 1, iluid is displaced under resistance of a spring loaded valve22 through a series of axially extending ports (not shown) from thelower chamber 15 of the shock absorber into the upper chamber 14, andfluid that is displaced by the volume -of the piston rod 13 in thechamber 14 escapes under resistance through the foot valve assembly 17into the reservoir chamber 21. On the rebound stroke of the piston 12,that is when the piston travels upwardly in the cylinder 11, fluid isdisplaced from the upper chamber 14 into the lower chamber 15 through aplurality of axial ports (not shown) in the piston under the resistanceof a blow-oit resisting spring, and the fluid which was displaced fromthe chamber 15 due to the volumetric displacement of the piston rod 13returns into the chamber 15 from the lreservoir chamber 21.

In order to provide for cushioning of the shock absorber by affording acertain or predetermined Iamount of free travel of the piston during atleast the compression stroke thereof and preferably also during therebound stroke, an air pocket or cell is provided in association withthe upper chamber 14.

In the embodiment shown in Figure l this air pocket or cell forcushioning of the shock absorber comprises a ring-like air cellstructure 31 including .a generally channel-shaped annulus 32 openinginwardly and having oppositely extending generally axial annular flanges33 of a diameter to engage the outer wall surface of the cylinder 11 andsecured thereto as by means of brazing or welding 34. This provides anair cell space 35 encircling the upper end portion of the cylinder 11and communieating with the cylinder chamber 14 through a port 37.Thereby hydraulic fluid `displaced from the chamber 14 into the air cellchamber 35 through the port 37 will cause compression of air in the aircell space 35.

In order to avoid possible displacement of air from the air cell space35 int-o the cylinder chamber 14, the air or other gas within the aircell space is trapped within Ia sealed collapsible and preferablyresilient wall tubular cell member 38 which preferably substantiallyfills the chamber 35. The interior of the tubular cell member 38provides a hollow gas lled chamber 39.

Upon the development of pressure in the chamber 14, hydraulic fluiddisplaced through the port 37 into the air cell chamber 35 causes theflexible, resilient air cell 38 to 4collapse and compress the air or gasin the cell chamber 39, thus affording a certain amount of free travelof the piston 12 and cushioning ofthe action of the shock absorberduring both compression and rebound strokes.

The size of the port 37 will determine the extent of this end, the aircell structure 40 comprises an annular generally inwardly openingchannel-shaped body 41 having generally axially oppositely extendingflanges 42 which are secured as by welding or brazing 43 to the externalsurface .wall of the cylinder 11 adjacent to the 4bottom thereof andproviding an air cell chamber 44-therein which is sealed from thereservoir chamber 21 but-.has communication with the cylinder chamber 15`through a metering port 45. It will be observed that both the air cellcharnber casings 32 and 41 are of smaller .diameter `than the internaldiameter of the reservoir casing tube 2t) so as to permit hydraulic uidto be displaced thereby inthe reservoir chamber.

For .trapping the air or gas in the air cell chamber 44 to avoiddisplacement thereof intothe cylinder, a tubular resilient, collapsibleannular cell member 47 is .provided which substantially lls the chamber44, and providesan air or gas chamber 48. EDuring a compression strokeof the piston 12 hydraulic lluid is displaced throughthe port 45 intothe air cell chamber 44 and collapses the air cell member 47 andcompresses the gas in the chamber 48, thereby Iproviding a cushion andcertain amount of free travel of the piston 12 during the ycompressionstroke.

In the form of Figure 2s, a direct :actingor'telescopic shock absorberis shown in which the basic features of the shock absorber aresubstantially the same as in the form of Figure l and similarreferencenumerals have been applied to indicate similar parts. In thisform of the invention, however, cushioning air cell structuresareprovided wherein air isolating casings or tubes are omitted. To thisend, an air cell structure 50 may be provided for the upper chamber 14ofthe shock absorberand cornprises an annular inwardly openingchannel-shapedsubstantially rigid casing ring 51 having opposite axiallyextending attachmentflangcs 52 which are securedlas by means of weldingor brazing 53 to the outer surface of the cylinder 11 to kprovide .asealedair chamber .5.4 encircling the cylinder at the upper end of thechamber 414. Communication with'the chamber 14 iseffected from the n ircell chamber 54.through `a port 55 which is located at the lowermostportion of the chamber 54.

Through `this arrangement, upon the development of pressure within thechamber 14, hydraulic tluid displaced through the port 55 into the airchamber54 causes air in the chamber 54 to be compressed .intothe upperportion of the chamber 54. Upon release of` the pressure the. airexpands and cxpels the hydraulic fluid from the chamber 54 through theVport 55. The size ofthe port 55 will determine the .extentof meteringof the hydraulic fluid and thus supplements the cushioning resistanceand smoothness of the action of the shock absorber Jin service. The sizeof the air cell chamber 54 will determinethe extent of the free travelof the kpiston 12 during lacornpression or rebound stroke.

Alternativelytopr supplementary to the air `cell Si), there may beprovidedan air cell structure 57 in association with the lower pressurechamber .15 vofthe `shock absorber. For .this ,purpose `an annular,substantially rigid, andpreferably lsheeletmletal ring casingSS ofYgenerally channel shape ,with g 4the s channel ,opening inwardly isprovided encircling Vthe cylinder l 1.1,,preferab'lyladjacent to itslower end` and thusatthelower end of the-chamber l5. The aircellfcasing. ring Sissecilred tothe cylinder l1 by means ofaxiallyoppositely Eextending marginal llanges 59 lwhich .aresecured to`theouter.surfaceofthe cylinder lasby means ot brazing orweldingotl toprovide atluid-tight seal.

Communication between the chamber andan air cell space or chamberlwithin the cell casing 58 is provided for by a port 62 atlthe lowerportion of .themchamlber161- As a result, upon the development ofcompressions/trol@ pressure within the chamber n15hydraulic fluid `willbe displaced through the port .62,vand intothe air cell chamber-61,andeectcompression ofairin the` air cell space and afford a free travel,cushioning in operation of the shock absorber.

It will be observed that the air cell 57 is shown as of substantiallysmaller volume than the upper cell 50. For supplementary purposes, thisissatisfactory since both the air cell ,Sprand thesaircell 57 areoperative for cushioning purposes during a compression stroke. Where thelower or compression stroke effective air cell 57 alone is used,itmaybedesired tolhave the same of larger size, but that is .afmatter ofchoice `to -be determined by the operating characteristics desired forany particular service conditions that must be .metby the shockabsorber. It may also be noted that the sizeof the port 62 is smallerthan the portJSso that a greater pressure drop in the metering of thehydraulic lluid through the port 62 is afforded.

Where, as shown in the drawings, the shock absorber is provided with asurge baille ring 63, it is desirable to mounttheballleringon thecylinder 11 rather than on the inside of theyreservoir casing tube Z0 asis the usual l practice. This facilitates assembly of the shock absorbercomponents.

The shock absorber also includes the usual top structure including@ topclosuredisk 64 providing a bearing forthe piston rod 13, as well as apacking gland structure 65 through .which .the .piston rod 13 isoperable above the closure disk 6.4. A gravel guard 67 may also beprovided.

` Theterm airw here used vherein should be construed tomean any gaseousmedium, although it will be evident thatyin thestruvctures disclosedherein air as such will be the usuahand economically uavailable gaseousmedium for the` air cell chambers.

It will, be understood .thaty modications and variations may he effectedwithout departing from the scope of the novel concepts of, the V.presentinvention.

We claimas our invention:

,1. ,In a direct `acting shock absorber assembly includging a vcylinderhaving ,a piston operable therein and a reservoir tube encircling-thecylinder and alfording therewitha reservoirchamber, an air cellcushioning structure in the reservoir chamber and communicating with theinterior of the cylinder but non-communicating with the reservoirchamber.

2. In combination in a hydraulic shock absorber comprising a cylinder, apiston operable in the cylinder, the piston having a piston rodextending through one portion of the cylindermeans providing a reservoirchamber in communication withsaid cylinder, hydraulic lluidsubstantially filling the cylinder, and a cushioning aircell structureconcentrically encircling the piston rod and subjected to hydraulicfluid upon the development of pressure in the cylinder ,during acompression stroke, said air cell structurencomprising a casingencircling the cylinder and having portcoinniunication with the interiorof the .cylinder'lbut,noncnimunicating with said reservoir chamber.

3. flncombignation yin .a hydraulicshock absorber comprising a cylinder,a piston loperablein the ycylindenthe piston lhaving zal piston rodextending through .one portion of the cylinder, nnea'ns .providing areservoir cha'mbcnin communication ,with said cylinder, hydraulic lluidsubstantiallyillingnthe cylinder, and a cushioning airV cell structureconcentrically encircling the piston ,roldzand subjected Ato hydraulictlid upon thedevelopment of pressure inuthecylindernduring a compressionstroke, said air .cell

structure comprising a substantially rigid casing encircling the shockebsorbrcylinder and having a yllexible `air isolating ,tube therein[and a port communicating withthe interior of the rigid casing yfordisplacement of hydraulic fluidunder pressure into the casing forcompressing ysaid tube but, non-communicating with said reservoirchamber.

A.,Incombinationginva hydraulic shock absorber inclrurlxingacylinderlandfapiston operable in the cylinder andcdividing.thecylinde'rinto compression stroke and rebound .stroke .chamber portions, meansproviding a reservoir chamber vin communication with said cylinder,

and an annular air cell structure for cushioning the compression strokeof the piston in hydraulic fluid pressure relation to the compressionstroke chamber portion of the cylinder, said air cell structurecomprising a casing disposed about the cylinder and having portedcommunication with the interior of the cylinder but non-communicatingwith said reservoir chamber.

5. In combination in a hydraulic shock absorber including a cylinder anda piston operable in the cylinder and dividing the cylinder intocompression stroke and rebound stroke chamber portions, means providinga reservoir chamber in communication with said cylinder, and an annularair cell structure for cushioning the compression stroke of the pistonin hydraulic fluid pressure relation to the compression stroke chamberportion of the cylinder, said air cell structure comprising a fullysealed air cell member of flexible material and a casing supporting thesame about the exterior of the cylinder noncommunicating with thereservoir chamber but communicating with the interior of the cylinderthrough a iluid port for subjecting said exible casing to hydraulicfluid under compression stroke pressure.

6. In a direct acting shock absorber including a cylinder and a pistonoperable in said cylinder in the presence of hydraulic fluid in thecylinder, a cushioning air cell structure of generally ring form andsubjected to hydraulic fluid pressure during a compression stroke of thepiston in the cylinder, said air cell structure having an air chambertherein within which the air is compressible to atord a limited amountof free travel of the piston during the compression stroke, said aircell structure comprising a substantially rigid casing secured about thecylinder and communicating through a port in the wall of the cylinderwith one end of the cylinder but non-communicating with the other endthereof, said casing having a flexible air cell member enclosing the airwithin said chamber.

7. In a direct acting hydraulic shock absorber including a cylinder anda piston operable in the cylinder and dividing the cylinder intocompression stroke and rebound stroke chamber portions, a generallychannelshaped inwardly opening annular casing secured in fluid tightrelation about the exterior of the cylinder in the region of the reboundstroke chamber portions and including an annular resilient air cellcushioning structure disposed within the annular casing and exposed tohydraulic tluid pressure that develops in said rebound stroke chamberportion in the operation of the piston but nonexposed to pressure of thecompression stroke chamber of the cylinder, and a second generallychannel-shaped inwardly opening annular casing secured in tight iluidrelation about the exterior of the cylinder in the region of thecompression stroke chamber and including a resilient annular air cellcushioning structure carried within said second channel shaped casingand exposed to hydraulic iluid pressure vthat develops in saidcompression stroke chamber portion in the operation of the piston butnon-exposed to pressure of the rebound stroke chamber of the cylinder.

References Cited in the tile of this patent UNITED STATES PATENTS1,565,770 Almesan Dec. 15, 1925 1,936,788 Hardy Nov. 28, 1933 1,953,128Peteler Apr. 3, 1934 2,571,279 Myklestad Oct. 16, 1951 2,628,692 HufierdFeb. 17, 1953 2,668,604 Chisholm Feb. 9, 1954 2,701,714 Harwood Feb. 8,1955 FOREIGN PATENTS 296,897 Great Britain Sept. 13, 1928

